This invention relates to carboxyphosphonates and their use as brush control agents. The use of various carbamoylphosphonates for control of plant growth is known in the art. For example, U.S. Pat. No. 3,627,507 and German Offenlegungsschrift No. 2,040,367 relate to the use of carbamoylphosphonates for plant growth control. However, neither of these references suggest the carboxyphosphonates of this invention. Berichte 57, 1023 (1924) describes trisodium carboxyphosphonate as well as the zinc, manganese, copper, lead and silver salts. However, this reference does not describe any utility for these salts.